820-3437 fan 5 sec and shutdown

[raainxx]

Hi
i have this macbook air where i find a liquid spill on R7611,R7612 & C7615 on P1V05_S0_VREF, i change all this component but the problem is same, fan start 5 sec & shutdown
P1V05_S0_VREF fall 1,043V to 0V when the mac shutdown.
I don't find where P1V05_S0_VREF is generate, do you know?
thanks

 

[dukefawks]

Is Vcore present when the fan spins? Does it shutdown and power on again?

 

[raainxx]

I check tomorow for the Vcore but no shutdown and stay off, but when i short power pad, he start again.

 

[raainxx]

when you say VCORE, is it PPVCC_S0_CPU = 1,74V and fall when fan stop.
The led is orange without battery

 

[dukefawks]

Could be anything. Corrosion under SMC, traces U1900 to Y1905? JTAG?

 

[raainxx]

Corrosion near Q8150 is it cause my problem?
thanks

 

[smiba]

Possibly, Q8150 is there for the ALL_SYS_PWRGD signal.

 

[rvanpruissen]

Is the keyboard disconnected when you try?

 

[raainxx]

ALL_SYS_PWRGD climb to 3,34 and fall at 0V.
i disconnect keyboard, only magsafe board with cable left board and power adapter.

 

[Gurmon]

There's going to be corrosion somewhere. Time to inspect visually for damage.

 

[raainxx]

I inspect all the board under microscope, i put the board in ultrasound cleaner, the board is clean, no corrosion on the board.
i check with scope the signal Y1905 ok i have SYSCLK_CLK25M_X2 at 25mhz but nothing in output of U1900, all PP3V42_G3H=PP3V3_S5=PP3V3_S5RS3RS0_SYSCLKGEN=3,34V during my board is ON.
is it U1900 bad?
thanks

 

[dukefawks]

U1900 is fine as the only output needed to work is 32kHz on pin 12. Without that the board would not even power on.

Does it stay on for 5 seconds then off and then repeat forever?

 

[raainxx]

i have in fact the clock in pin 12 32Khz and always on but the board start and shutdown.
i can't find where is the problem?

 

[dukefawks]

I ask again: Does it stay on for 5 seconds then off and then repeat forever or just stay off?

 

[raainxx]

no just stay off, if i want to restart the board i need to short the power pad.

 

[dukefawks]

Either crap under SMC or the termination resistors/traces from U6100 to SMC.